Process for producing pure benzene hydrocarbons



Marh24,1942.1 H, KRUGER HAL 2,277,115

PROCESS FOR PRGDUCING PURE BENZENE HYDROCARBONS Filed Aug. 4, 1938 2 sheets-sheet 1.

ATTORNEY.

H. KRUGER ETAI..

` March 24, 1942.

PROCESS FOR PRODUCING PURE BENZENE HYDROCARBONS 2 'sheets-sheet 2- Filed Aug. 4, 1938 Patented Mar.V 24, 1942 PROCESS FOR PBODUCING PRE BEZENE HYDBOCARBONS Hugo Krger, Gottesberg, Kreis Waldenburg in Schlesien, and Kurt Gieseler, Hermsdorf, Kreis Waldenburg in Schlesien, Germany, assignors` to Sherka Chemical Co. Inc., Bloomlield, N. J., a corporation of New York Application August 4, 193s, sei-m No. 223,07

In Germany August 5, 1937 comms. (ci. 2oz-c7) This invention relates to a. process for the' manufacture of pure hydrocarbons of the benzene series.

In order to produce pure benzene, pure toluene, C

pure xylene or other hydrocarbons of the benzene series in general'one has hitherto proceeded in such a manner that the crude or puried benzene, toluene or xylene fractions obtained by fractionation, after washing with concentrated sulphuric acid, were subjected to a very careful discontinuous distillation which was finally carried out in horizontal stills which were providedwith -high columns. There are thereby always produced considerable quantities of intermediate fractions, first and after runnings so that the yields of pure hydrocarbons did not amount to more than 80%.

Continuous distillation for the production of motor benzol has heretofore been carried outin such a manner that with removal of an initial fraction and a residual fraction, an intermediate usable motor benzol with boiling limits of 80- 150 C. has been obtained. Recently it has also been possible by means of continuous distillation of light oils to obtain toluene almost quantitatively in the form of crude or purified toluene with boiling limits of 10G-120 C.

Hitherto, however, it has not been possible, on a commercial scale by means of continuous distillation in a progressive distillation operation and without the occurrence of intermediate fractions to obtain pure hydrocarbons such as Pure benzene, boiling to the extent of 90% within 0.6 C. and to the extent' of 95% within 0.8 C.,

Pure toluene, boiling to the extent of 90% within 0.6 C. and to the extentvof 95% \within 0.8 C., or i Pure xylene, boiling to the extent of 90% within 3.6 C. and to the extent of 95% within 4.5" C. It is true that the Kubierschky column ha been recommended for the continuous separation of benzene, toluene and xylene (Lunge-Khler, Die Industrie des Steinkohlenteers und des ence to theaccompanying drawings which illus- Ammoniaks" vol. 1, 1912, Page 897); there is.

of consecutive columns according to the present 55 invention and by selection of a suitable composition of the starting material, there is obtained in a continuous distillation operation without any intermediate fractions, in the form of standard pure hydrocarbon, -95% of the, pure hydrocarbon present in the starting material.

The invention is described below with refertrate diagrammatically arrangements of stillsA for carrying out the present process in-which like reference characters indicate like parts.

Fig. 1 is a diagrammatic view of any apparatus adapted for carrying 'out the p'resent process, and

Fig. 2 is a similar view showing a modified apparatus for carrying'out a modication of the present process.

Referring to Figure 1, the crude product, washed with caustic soda lye and sulphuric acid, is preheated and introduced at a into the column I to about 1/2 to 2A, of the height. The column l contains fractionating coils divided into two sections, which-in the bottom part are heated with steam, and consist to the extent of 1/2 to 2A; of vaporizing coilsand tothe extent of 1/3 to 1/2 of rectifying coils. In this column all constituents b boiling lower than the hydrocarbon to be produced are distilled ofi and the hot residue c leaving the column 1' through a pipe is continuously delivered by. means cf the pump P to the column 2. The column 2 contains as many 4 or imore rectifylng coils than vaporizing coils so thatv the pure hydrocarbon d distils oi within the required boiling limits and is separated from the residue which leaves at r.

In order to attain in the column I the complete separation of all constituents boiling lower` than the pure hydrocarbon to be produced, the liquid residue flowing oif from the column must have a boiling point which in the case of pure benzene manufacture amounts to at least 86 C. and in the case of the manufacture of pure toluene amounts to at least 115 C., that is to say about 5 C. above the boiling point of the pure hydrocarbon to be produced. If this isl not the case then the lower boiling constituents cannot be distilled off .without residue and the lower boiling limit of the pure hydrocarbon to be produced is too low. It is necessary either to select the composition of the starting material such that for example the crude toluene boils to the extent of between 10D-130 C. and contains at least 10% Xylenes or care must be takenl by the admixture of. higher boiling constituents that the residue from the rst column has the necessary high boiling polntand is obtained from the required boiling point, or a puried toluenewhichstill contains aconsiderable proportion of paran hydrocarbons such as` heptane or octane, it has proved to be advantageous to attach to the main columns in each case an auxiliary column (Figure`2). Together with the column I thus the lateral column A is operated. To this latter is supplied a denitely adjustable proportion e of the residue from the former column I, for example lil-% of the original quantity a, which is withdrawn from one or more still sections, consisting of about y, benzene and toluene and thus containing all the heptane. This portion e is separated in the auxiliary column A into benzene with heptane f and a considerably concentrated toluene, about 98%, g which is either mixed again with the product to be worked up i. e. the column ,I or employed in some other way. The distillates of the two columns b and j are combined. A

The liquid residue c from column I is free from all constituents boiling lower than toluene and is forced by means of the pump P continuously through the heater D into the column 2 in which as distillate d pure toluene is obtained. In the case of the presence of substances which boil between toluene and xylene a certainproportion h of the residue from the column 2 is drawn oil' laterally from the still sections and supplied to the auxiliary column B in which as distillate i pure toluene is also produced while the residue is combined with that from 2. In this'manner there is obtained by means of the continuous distillation, even in the case of working up of crude toluene boiling between 100 and 120 C. or toluene containing paraiiin hydrocarbons, a pure toluene in a yield of over 90%.

While we have herein shown and described certain preferred embodiments of our invention, we wish it to be understood that we do not confine ourselves. to all the precise details herein set forth by'wayof illustration, as modification and variation may be made without departing from the spirit of the invention or exceeding thescope of theappended claims.

What we claim is:

1. A process for the production of a pure hydrocarbon taken from the class consisting of benzene, toluene, and xylenes from crude liquid mixtures with other'hydrocarbons of the benzene series which comprises introducing into the rectincation zone of a 'column' such a crude mixture together with higher boiling hydrocarbon constituents, the latter being in suflcient amount to raise the boiling range of the mixture (after vaporization of constituents boiling below said r fying zones in said column, causing vaporization of substantially all of the lower boiling hydrocarbons until the liquid residue in said column' has a boiling range substantially above the boiling point of the pure hydrocarbon to be produced, passing said residue into a second column and causing vaporization of said hydrocarbon from said residue, and condensing the pure vapors of the desired hydrocarbon.

2. A process for the production of a pure hydrocarbon taken from the class consisting of benzene, toluene, and xylenes from crude liquid mixtures with other hydrocarbons of the benzene series which comprises introducing into the rectiilcation zone of a column such a crude mixture together with higher boiling hydrocarbon constituents, the latter being in sufiicient amount to raise the boiling 4range of the mixture (after vaporization of constituentsv boiling below said pure hydrocarbon) suiiiciently above the normal .boiling point of said pure hydrocarbon to substantially prevent distillation of said pure hydrocarbon during said vaporization, subjecting the same to the action of vaporizing and rectifying lzones in said column, causing vaporization of substantially all of the lower boiling hydrocarbons untilthe liquid residue in said column has a boiling range of atleast 5 C. above the boiling point of the pure hydrocarbon to be produced,

passing said residue into' a second column and causing vaporization of said hydrocarbon from flcation zone oi a column such a crude mixture together with higher boiling hydrocarbon constituents, the latter being in suicient amount to raise the boiling range of the mixture (after vaporization of constituents boiling below said pure hydrocarbon) suiilciently above the normal boiling point of said pure hydrocarbon to substantially prevent distillation of said pure hydrocarbon during said vaporization, subjecting the same to the action of vaporizing and rectifying zones in said column, the vaporizing zone being greater in extent than the rectifying zone, causing vaporization of substantially all of the lower boiling hydrocarbons untilthe liquid residue in said column has a boiling range of at least 5 C'. above the boiling point of the pure hydrocarbon tobe produced, passing said residue into a second column and causing vaporization of said hydrocarbon from said residue, and condensing the pure vapors of the desired hydrocarbon.

4. A process for the production of a pure hydrocarbon taken from the class consisting of benzene, toluene, and xylenes from crude liquid mixtures with other hydrocarbons of the benzene series which comprises introducing into the rectication zone-of a column such a crude mixture together with higher boiling hydrocarbon constituents, the latter being in suilicient amount to raise the boiling range of the mixture (after vaporization of constituents boiling below said purev hydrocarbon) suillciently above the normal boiling point of said pure hydrocarbon to substantially prevent distillation of said pure hydrocarbon during said vaporization, subjecting the same to the action of vaporizing and. rectifying `zones insaid column, the vaporizing zone being greater in extent than the rectifying zone, causing vaporization of substantiallyall of the lower boiling hydrocarbons until the liquid residue insaid column has a boiling range at least 5 C. above the boiling point of the-purehydrocarbon to be produced, passing said residue into a second column having yrectifying and vaporizing zones, the rectifying zone being greater in extent than said hydrocarbon from said residue, and condensing the pure vapors of the desired hydrocarbon.

5. A process for the production of pure benzene from crude liquid mixtures thereof with other i hydrocarbons of the same series which comprises providing such a mixture together with higher boiling hydrocarbon constituents, providing such higher boiling constituents in sufficient amount to raise the boiling range of said hydrocarbon mixture sufiiciently above the normal boiling .point of benzene to substantially prevent distillation thereof during vaporization of lower boiling constituents of said mixture, introducing said mixture into the rectification zone of a co1- umn, subjecting the same to the action of vaporizing and rectifying zones in `said column,l

causing vaporization of substantially all of the lower boiling hydrocarbons until the residue in said column has a boiling range of at least 86 C., passing said residue `into a second column and causing vaporization of benzene from said residue, and condensing the'pure benzene.

6. A process for the production of pure toluene from crude liquid mixtures thereof with other -hydrocarbons of the same series which comprises providing such Aa mixture together with higher boiling hydrocarbon constituents. providing such higher boiling constituents in sufiici'ent amount to raise the boiling range of said hydrocarbon mixture sufficiently above the normal boiling pointl of toluene to vsubstantially prevent distillation thereof during vaporization of lower boiling constituents of said mixture, introducing said mixture into the rectication zone of a column, subjecting the same to the ,action of vaporizing and rectifying zones in said column, causing vaporization of substantially all of the lowerboiling hydrocarbons until the residue in said column has a boiling range of at least 115 C., passing said residue into a second column and `causing vaporization of toluene from said residue, and condensing the pure toluene.

HUGO KRGER. KURT GIESELER. 

